Introduction to usability

1. Media Design course
Autumn 2016
Evaluation Methods
Usability

2. INDEX
1. Introduction
2. Usability metrics
3. Usability inspection methods
4. User-based evaluation
5. Usability evaluation methods
6. Planning evaluation

3. 1. INTRODUCTION
The effectiveness, efficiency and satisfaction with which specified
users achieve specified goals in particular environments.
Definition of usability
ISO/IEC 9126

4. 1. INTRODUCTION
Usability quality components (Nielsen, 2012)
• Learnability
• Efficiency
• Memorability
• Errors
• Satisfaction

5. User behavior has low tolerance for difficult designs or slow sites. If they don’t
understand the functioning of the sites, they will leave.
Why investing in usability?
1. INTRODUCTION
• Offer a good return on investment
• Can bring competitive advantage
• Help making the design adequate.
Usability studies:

6. EFFECTIVENESS
The accuracy and completeness with which users achieve specified goals
Usability metrics (ISO/IEC 9126-4 – Metrics)
• Completion rate
• Number of errors
Errors can be unintended actions, slips, mistakes or omissions that a user makes
while attempting a task. Errors detected during user testing should be described,
rated and classified.
2. USABILITY METRICS

7. Usability metrics (ISO/IEC 9126-4 – Metrics)
• Overall relative efficiency
The overall relative efficiency uses the ratio of the time taken by the users who successfully
completed the task in relation to the total time taken by all users.
2. USABILITY METRICS
EFFICIENCY
The resources expended in relation to the accuracy and completeness with which
users achieve goals.
• Time-based efficiency
This value helps identify the average time spent on a task (which might be successfully
completed or not)

8. Usability metrics (ISO/IEC 9126-4 – Metrics)
2. USABILITY METRICS
SATISFACTION
The comfort and acceptability of use.
• Task level satisfaction
Just after users attempt a task they should be given a questionnaire to measure how difficult
that task was.
A popular post-task questionnaire is the SEQ (Single Ease Question) consisting in 1 question.

9. 2. USABILITY METRICS
• Test level satisfaction
At the end of the test, each participant fills a questionnaire to assess their general level of
satisfaction
1. I think that I would like to use this system frequently.
2. I found the system unnecessarily complex.
3. I thought the system was easy to use.
4. I think that I would need the support of a technical person to be able to use this system.
5. I found the various functions in this system were well integrated.
6. I thought there was too much inconsistency in this system.
7. I would imagine that most people would learn to use this system very quickly.
8. I found the system very cumbersome to use.
9. I felt very confident using the system.
10. I needed to learn a lot of things before I could get going with this system
SYSTEM USABILITY SCALE

10. User experience is concerned with “all aspects of the user’s experience when
interacting with the product, service, environment or facility
User experience versus user satisfaction
ISO 9241-210
2. USABILITY METRICS

11. 3. USABILITY INSPECTION METHODS
• Heuristic evaluation
• Cognitive walkthrough
Experts assessment
• Feature inspection
• Consistency inspection
• Standards inspection

12. 3. USABILITY INSPECTION METHODS
Heuristic evaluation
• Systematic inspection method of the GUI
• Check if basic design rules have been
followed appropriately
• Goal is to find usability problems
• Carried out often before the user test
• Evaluators go trough the list of ten rules (principles)
http://www.melodychou.com/spoter.html

13. 3. USABILITY INSPECTION METHODS
Heuristic evaluation (Normal Nielsen group)
• Use of simple and natural dialogue
• Speak the users language
• Minimise users’ memory load
• Make user interface consistent
• Give user feedback
• Mark exits clearly
• Make shortcuts available
• Give clear error messages
• Prevent errors
• Provide enough help and documentation

14. 3. USABILITY INSPECTION METHODS
• Cognitive walk through is useful to understand the user's thought processes
and decision making when interacting with a system, specially for first-time
or infrequent users.
• Aim is to “walk trough” all the tasks in the service that the users is supposed
to perform.
Cognitive walkthrough
Pluralistic usability walkthrough
• The service is gone trough with experts and the designers, users and they
discuss the elements

15. 4. USER-BASED EVALUATION
The purpose of user testing is not to understand users but to evaluate
how particular users can carry out particular tasks (using your system)
in a particular context.
Aim
User testing followed by a single design iteration improves
measured usability by 38% on average

16. 4. USER-BASED EVALUATION
Validity versus reliability
Reliability
Validity
• Does the usability test measures something of relevance to usability of real products
in real use?
• Requires methodological understanding of the test method
• Typical problems deal with user selection, task selection, omitting time constraints
and social influences.
• Would the same results be obtained if the tests were repeated?
• Reliability of usability tests is a problem because of the huge individual differences
between test users.

17. Types:
Formative
Summative
4. USER-BASED EVALUATION
• Can take place at any point during development.
• The focus is to identify problems and potential solutions (possibly with indication of
frequency).
• The designers can then use these frequencies to help rate the severity of the
problems and prioritise.
• Assesses the success of a finished system or product (find fixes before release and
assess future releases)
• The performance levels are measured using a set of predefined benchmark tasks.

18. Usability benchmarking
Basic usability study measurements:
• Success/Failure within a time threshold
• Time on task
• # of errors before completion
4. USER-BASED EVALUATION
Image from Flickr user “Josep Ma Rosell”

19. Usability-lab studies
4. USER-BASED EVALUATION
Usability-Lab Studies: participants are brought into a lab, one-on-one with a researcher, and given a
set of scenarios that lead to tasks and usage of specific interest within a product or service.
Image from Flickr user “Yandle” Image from Flickr user “Witflow”

20. Eyetracking
4. USER-BASED EVALUATION
An eyetracking device measures where participants look as they perform tasks or interact naturally with
websites, applications, physical products, or environments.
https://www.flickr.com/photos/cinteractionlab/4557712520
https://www.flickr.com/photos/rosenfeldmedia/10910197294

21. Card sorting
4. USER-BASED EVALUATION
Users are asked to organize items into groups and assign categories to each group.This method
helps create or refine the information architecture of a site by exposing users’ mental models.
Image from Flickr user “Yandle”

22. Remote studies
• Moderated remote usability studies
Studies conducted remotely with tools such as screen-sharing and remote control capabilities.
• Unmoderated remote panel studies
Trained participants who have video recording and data collection software installed on their own personal
devices use a product while thinking aloud.
• Unmoderated UX studies
Research tool installed on participants devices that captures behaviors and attitudes, usually by giving users goals
or scenarios to accomplish
• True-intent studies
Random site visitors are asked about their goals on a site and how successfully they were.
• Intercept surveys
A survey that is triggered during the use of a site or application.
4. USER-BASED EVALUATION

23. Clickstream analysis
4. USER-BASED EVALUATION
Analysis of the record of screens or pages that users clicks on and sees, as they use a site or
software product; it requires the site to be instrumented properly or the application to have
telemetry data collection enabled.
http://www.userzoom.com/ux-benchmarking/7-reasons-why-userzooms-mobile-solution-makes-usability-benchmarking-
easy-and-efficient/

24. A/B testing
4. USER-BASED EVALUATION
Testing different designs on a site by randomly assigning groups of users to interact with each of the
different designs and measuring the effect of these assignments on user behavior.
http://ecommerceconsulting.ca/2012/07/five-best-tools-for-ecommerce-diagnostics-part-2/

25. Think aloud protocol
4. USER-BASED EVALUATION
A verbal protocol used to understand what users are thinking while they are performing tasks.
Verbal protocol has negative impacts on many measurable user performance metrics, such as time
to complete tasks.
https://www.youtube.com/watch?v=-h8hUtwkMCE

26. Wizard of Oz
4. USER-BASED EVALUATION
Research experiment in which subjects interact with a (computer) system that subjects believe to
be autonomous, but which is actually being operated or partially operated by an unseen (hidden)
human being.
http://www.ericsson.com/uxblog/2012/12/smokes-and-mirrors/

27. A cost-effective method proposed by Jakob Nielsen of usability evaluation based on
three techniques:
• Scenarios
Discount usability engineering
• Simplified think-aloud
• Heuristic evaluation
5. USABILITY EVALUATION METHODS
The primary characteristics of discount usability engineering are small sample sizes,
frequent repetition of these small tests, and reliance on direct observations rather than
on statistically established findings.

28. 6. PLANNING USERTESTING
1. Purpose of the test (formative/summative evaluation)
2.Test goals (ex: overall usability, learnability, errors…)
3. Users
Who are the users going to be and how are we going to get hold of them?
How many users are needed?
5.Tasks
What test tasks will the users be asked to perform?
What criteria will be used to determine when the users have finished each of the test tasks correctly?
To what extend will the experimenter be allowed to help the users during the test?
4. Organization
Who will facilitate the test?
Where will the test take place? What equipment is required? How long it will take?...

29. 7. Data collection
What data is going to be collected?
What data collection instruments will be used?
8. Data analysis
What evaluation measures will be used?
What data analysis methods will be adopted?
6. Methods
What methods are going to be used?
6. PLANNING USERTESTING
Ethical aspects
Provide enough information to the participants (take informed written consent)
Participants should be aware that they can withdraw at any point
Participants’ data should be anonymized

30. Background information
How much does the user know about the product?
User background information (age, occupation…)
Before the test
Providing information to the user (what is the test about, aims, structure of the session…)
Make clear:
-The purpose is to evaluate the software, not the user
- All information is confidential
-The user may pause or stop the test at any given moment
6. PLANNING USERTESTING
Test stages

31. During the test
The user should have feeling of control
Create a scenario of what the user should do i.e., tasks
Tasks are usually given one at time
Natural tasks
Observe, ask, give guidance when needed
6. PLANNING USERTESTING
Test stages
After the test
Debriefing
Questionnaire Image from Flickr user “Leandro Agrò”

32. FURTHER READINGS
This material uses Creative Commons License
Recognition – Share alike.
Brooke, J. (1996). SUS-A quick and dirty usability scale. Usability evaluation in industry, 189(194), 4-7.
Cockton, G. Usability evaluation. Interaction Design Foundation.
https://www.interaction-design.org/literature/book/the-encyclopedia-of-human-computer-interaction-2nd-ed/usability-evaluation
Cooper,A. (2004). The inmates are running the asylum:[Why high-tech products drive us crazy and how to restore the sanity].
Indianapolis, IN, USA:: Sams.
Dumas, Joseph S. and Redish, Janice C. (1993):A Practical Guide to UsabilityTesting. Norwood, NJ, Intellect
Forlizzi, Jodi (2008):The product ecology: Understanding social product use and supporting design culture. In International
Journal of Design, 2 (1) pp. 11-20
Gould, J. D., Lewis, C. (1985). Designing for usability: key principles and what designers think. Communications of the
ACM, 28(3), 300-311.
International Standards Association (2001). ISO/IEC 9126-1:2001 Software engineering - Product quality - Part 1: Quality
model,. Retrieved 1 December 2011 from International Standards Association:
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=22749

33. FURTHER READINGS
This material uses Creative Commons License
Recognition – Share alike.
International Standards Association (2004). ISO/IECTR 9126-4:2004 Software engineering -- Product quality -- Part 4: Quality
in use metrics. Retrieved 1 December 2011 from International Standards Association:
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39752
International Standards Association (2011). ISO/IEC 25010 Systems and software engineering -- Systems and software Quality
Requirements and Evaluation (SQuaRE) -- System and software quality models. Retrieved 1 December 2011 from International
Standards Association: http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=35733
Lavery, D., Cockton, G., and Atkinson, M. P. 1996. Cognitive Dimensions: Usability Evaluation Materials,Technical Report
TR-1996-17, University of Glasgow.Accessed 15/9/11 at http://www.dcs.gla.ac.uk/asp/materials/CD_1.0/materials.rtf
Lavery, D., and Cockton, G. 1997. Cognitive Walkthrough: Usability Evaluation Materials,Technical ReportTR-1997-20,
Department of Computing Science, University of Glasgow. Edited version available 15/9/11 as
http://www.dcs.gla.ac.uk/~pdg/teaching/hci3/cwk/cwk.html
Nielsen, J. (1994). Guerrilla HCI: Using discount usability engineering to penetrate the intimidation barrier. Cost-justifying
usability, 245-272.
Nielsen, J., Molich, R. (1990, March). Heuristic evaluation of user interfaces. In Proceedings of the SIGCHI conference on
Human factors in computing systems (pp. 249-256).ACM.

34. FURTHER READINGS
This material uses Creative Commons License
Recognition – Share alike.
Nielsen, J.; Norman, D.A. (14 January 2000). Web-Site Usability: Usability OnThe Web Isn't A Luxury. JND.org.
http://www.jnd.org/dn.mss/usability_is_not_a_l.html
Nielsen, J. (4 January 2012). Usability 101: Introduction to Usability. Nielsen Norman Group
https://www.nngroup.com/articles/usability-101-introduction-to-usability/
Nielsen, J. (1 January 1995).“10 Usability Heuristics for User Interface Design”. Nielsen Norman Group
https://www.nngroup.com/articles/ten-usability-heuristics/
Polson, P. G., Lewis, C., Rieman, J., Wharton, C. (1992). Cognitive walkthroughs: a method for theory-based evaluation of user
interfaces. International Journal of man-machine studies, 36(5), 741-773.
Ritter, F. E., Kim, J.W., Morgan, J. H., Carlson, R.A. (2013). Running behavioral studies with human participants:A practical guide.
Thousand Oaks, CA: Sage.
Whiteside, John, Bennett, John and Holtzblatt, Karen (1988): Usability Engineering: Our experience and Evolution. In: Helander,
Martin and Prabhu, PrasadV. (eds.). Handbook of human-computer interactio. pp. 791-817